Anti-fouling coatings fabricated from polymers containing ionic species

ABSTRACT

An anti-fouling coating is provided, containing a continuous matrix comprising a first component; a plurality of inclusions comprising a second component, wherein the first component is a low-surface-energy polymer having a surface energy, and the second component is a hygroscopic material containing one or more ionic species. The low-surface-energy polymer and the hygroscopic material are chemically connected ionically or covalently, such as in a segmented copolymer composition comprising fluoropolymer soft segments and ionic species contained within the soft segments. The continuous matrix and the inclusions form a lubricating surface layer in the presence of humidity. Coefficient-of-friction experimental data is presented for various sample coatings. The incorporation of ionic species into the polymer chain backbone increases the hygroscopic behavior of the overall structure. Improvement in lubrication enables material to be cleared from a surface using the natural motion of an automotive or aerospace vehicle.

PRIORITY DATA

This patent application is a non-provisional application claimingpriority to U.S. Provisional Patent App. No. 62/269,366, filed on Dec.18, 2015, and to U.S. Provisional Patent App. No. 62/269,984, filed onDec. 19, 2015, each of which is hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to anti-fouling materials,coatings, and systems.

BACKGROUND OF THE INVENTION

Coatings and materials can become soiled from debris (particles,insects, oils, etc.) impacting the surface. The debris affects airflowover the surface as well as aesthetics and normally is removed bywashing.

Many attempts are described to mitigate insect accumulation during theearly days of aircraft development. These include mechanical scrapers,deflectors, traps, in-flight detachable surfaces, in-flight dissolvablesurfaces, viscous surface fluids, continuous washing fluids, and suctionslots. The results of most of these trials were determined ineffectiveor impractical for commercial use.

Recently, Wohl et al., “Evaluation of commercially available materialsto mitigate insect residue adhesion on wing leading edge surfaces,”Progress in Organic Coatings 76 (2013) 42-50 describe work at NASA tocreate anti-insect adhesion surfaces. Wohl et al. tested the effect oforganic-based coatings on insect adhesion to surfaces, but the coatingsdid not fully mitigate the issue. Wohl et al. also describe previouslyused approaches to reduce bug adhesion such as mechanical scrapers,deflectors, paper and/or other coverings, elastic surfaces, solublefilms, and washing the surface continually with fluid.

One approach is to create a self-cleaning surface that removes debrisfrom itself by controlling chemical interactions between the debris andthe surface. Enzyme-filled coatings leech out enzymes that dissolvedebris on the surface. However, the enzymes are quickly depleted andcannot be refilled, rendering this approach impractical.Fluorofluid-filled surfaces have very low adhesion between impactingdebris and the surface. However, if any of the fluid is lost, thesurface cannot be refilled/renewed once applied on the vehicle, and thusloses its properties (see Wong et al., “Bioinspired self-repairingslippery surfaces with pressure-stable omniphobicity,” Nature 477,443-447, 2011).

Superhydrophobic and superoleophobic surfaces create very high contactangles (>150°) between the surface and drops of water and oil,respectively. The high contact angles result in the drops rolling offthe surface rather than remaining on the surface. These surfaces do notrepel solid foreign matter or vapors of contaminants. Once soiled byimpact, debris will remain on the surface and render it ineffective.Also, these surfaces lose function if the nanostructured top surface isscratched.

Kok et al., “Influence of surface characteristics on insect residueadhesion to aircraft leading edge surfaces,” Progress in OrganicCoatings 76 (2013) 1567-1575, describe various polymer, sol-gel, andsuperhydrophobic coatings tested for reduced insect adhesion afterimpact. The best-performing materials were high-roughness,superhydrophobic surfaces. However, they did not show that debris couldbe removed from the superhydrophobic surfaces once insects broke on thesurface.

Fluoropolymer sheets or treated surfaces have low surface energies andthus low adhesion force between foreign matter and the surface. However,friction between impacting debris and the surface results in thesticking of contaminants.

Polymeric materials having low surface energies are widely used fornon-stick coatings. These materials are tailored with careful control oftheir chemical composition (thus surface energy) and mechanicalproperties. Polymers containing low-energy perfluoropolyethers andperfluoroalkyl groups have been explored for low adhesion and solventrepellency applications. While these low-energy polymers facilitaterelease of materials adhering to them in both air and water, they do notnecessarily provide a lubricated surface to promote clearance foreignsubstances. See Vaidya and Chaudhury, “Synthesis and Surface Propertiesof Environmentally Responsive Segmented Polyurethanes,” Journal ofColloid and Interface Science 249, 235-245 (2002).

A fluorinated polyurethane is described in U.S. Pat. No. 5,332,798issued Jul. 26, 1994 to Ferreri et al. U.S. Pat. No. 4,777,224 toGorzynski et al. describes the process for the production of anionicpolyurethanes comprising aliphatic dihydroxy compounds (greater than 10carbon atoms), an aliphatic diol carrying an acid group, and apolyether. The polyurethane aqueous solutions are used for coating andsizing of paper. U.S. Pat. No. 4,956,438 to Ruetman et al. describes thecomposition and preparation of polyurethane ionomers synthesized bymaking an ionic prepolymer and chain-extending it with a polyolrequiring three or more reactive hydroxyl groups. U.S. Pat. No.7,655,310 to Trombetta describes polyurethanes containingperfluoropolyethers with ionizable groups such as a carboxylic acid oramine functionality for making waterborne systems. The patent alsodescribes the use of pendant silanes (i.e. trimethoxysilane groups) forcrosslinking the network. U.S. Pat. No. 6,992,132 to Trombetta et al.describes an aqueous dispersion of a linear crosslinkable ionomericpolyurethane containing carboxylic groups and having aperfluoropolyether structure and a crosslinking agent.

In view of the shortcomings in the art, improved coating materials andmaterial systems, and compositions suitable for these coating systems,are needed. Improvement in lubrication or decrease in the coefficient offriction would better enable material to be cleared from a surface usingthe natural motion of an automotive or aerospace vehicle.

SUMMARY OF THE INVENTION

The present invention addresses the aforementioned needs in the art, aswill now be summarized and then further described in detail below.

Some variations provide a segmented copolymer composition comprising:

(a) one or more first soft segments selected from fluoropolymers havingan average molecular weight from about 500 g/mol to about 20,000 g/mol,wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated;

(b) optionally, one or more second soft segments selected frompolyesters or polyethers, wherein the polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated;

(c) one or more ionic species contained within the soft segments and/orcontained in copolymer chains that are distinct from the soft segments;

(d) one or more isocyanate species, or a reacted form thereof,possessing an isocyanate functionality of 2 or greater;

(e) one or more polyol or polyamine chain extenders or crosslinkers, ora reacted form thereof.

In some embodiments, the fluoropolymers are selected from the groupconsisting of polyfluoroethers, perfluoropolyethers,polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof. Forexample, the fluoropolymers may include a fluoropolymer having thestructure:

wherein:X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50;m=1 to 100; andn=1 to 100.

When the one or more second soft segments are present, the polyesters orpolyethers may be selected from the group consisting ofpoly(oxymethylene), poly(ethylene glycol), poly(propylene glycol),poly(tetrahydrofuran), poly(glycolic acid), poly(caprolactone),poly(ethylene adipate), poly(hydroxybutyrate), poly(hydroxyalkanoate),and combinations thereof. The molar ratio of the second soft segments(when present) to the first soft segments may be less than 2.0.

In some embodiments, the ionic species are contained chemically withinthe first soft segments and/or within the second soft segments (ifpresent). In these or other embodiments, the ionic species are presentas, or in, polymer-chain pendant groups within the first soft segments.In these or other embodiments with the second soft segments present, theionic species are present as, or in, polymer-chain pendant groups withinthe second soft segments. In certain embodiments, the ionic species arecontained chemically in hard segments containing the reacted form of theone or more isocyanate species. Alternatively, or additionally, theionic species may be contained chemically in copolymer chains that aredistinct from each of the first soft segments, second soft segments, andhard segments.

The ionic species may be (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated, in some embodiments. The ionic species mayinclude a cationic species possessing a charge of +1 or more, or +2 ormore. The ionic species may include an anionic species possessing acharge of −1 or more negative, or −2 or more negative.

In some embodiments, the ionic species includes an ionizable salt orother ionizable molecule. In certain embodiments, the ionic speciesincludes a zwitterionic component. In some embodiments, the ionicspecies includes a polyelectrolyte or an ionomer.

The ionic species may be selected from the group consisting of2,2-bis-(1-(1-methyl imidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.

In some embodiments, the isocyanate species is selected from the groupconsisting of 4,4′-methylenebis(cyclohexyl isocyanate), hexamethylenediisocyanate, cycloalkyl-based diisocyanates, tolylene-2,4-diisocyanate,4,4′-methylenebis(phenyl isocyanate), isophorone diisocyanate, andcombinations or derivatives thereof.

The polyol or polyamine chain extenders or crosslinkers may have anaverage functionality of at least 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6,2.7, 2.8, 2.9, 3.0, or higher. The one or more polyol or polyamine chainextenders or crosslinkers may be selected from the group consisting of1,3-butanediol, 1,4-butanediol, 1,3-propanediol, 1,2-ethanediol,diethylene glycol, triethylene glycol, tetraethylene glycol, propyleneglycol, dipropylene glycol, tripropylene glycol, neopentyl glycol,1,6-hexane diol, 1,4-cyclohexanedimethanol, ethanol amine, diethanolamine, methyldiethanolamine, phenyldiethanolamine, glycerol,trimethylolpropane, 1,2,6-hexanetriol, triethanolamine, pentaerythritol,ethylenediamine,1,3-propanediamine, 1,4-buatendiamine,diethyltoluenediamine, dimethylthiotoluenediamine, isophoronediamine,diaminocyclohexane, N,N,N′,N′-tetrakis (2-hydroxypropyl)ethylenediamine, and homologues, combinations, derivatives, or reactionproducts thereof.

The composition contains, in a hard segment, the reacted form of the oneor more isocyanate species, combined with the reacted form of the one ormore polyol or polyamine chain extenders or crosslinkers, in someembodiments.

The segmented copolymer composition may be present in a coating or othersuitable material or object.

Some variations of the invention provide an anti-fouling coatingcomprising:

a substantially continuous matrix containing a first component;

a plurality of inclusions containing a second component, wherein theinclusions are dispersed within the matrix;

wherein one of the first component or the second component is alow-surface-energy polymer having a surface energy between about 5 mJ/m²to about 50 mJ/m², and the other of the first component or the secondcomponent is a hygroscopic material containing one or more ionicspecies,

wherein the low-surface-energy polymer and the hygroscopic material arechemically connected ionically or covalently,

and wherein the continuous matrix and the inclusions form a lubricatingsurface layer in the presence of humidity.

In some embodiments, the low-surface-energy polymer is a fluoropolymerselected from the group consisting of polyfluoroethers,perfluoropolyethers, polyfluoroacrylates, polyfluorosiloxanes, andcombinations thereof.

The ionic species may be selected from the group consisting of2,2-bis-(1-(1-methyl imidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.

In certain embodiments, the hygroscopic material consists essentially ofthe ionic species. In some embodiments, the hygroscopic material furtherincludes a material selected from the group consisting of poly(acrylicacid), poly(ethylene glycol), poly(2-hydroxyethyl methacrylate),poly(vinyl imidazole), poly(2-methyl-2-oxazoline),poly(2-ethyl-2-oxazoline), poly(vinylpyrolidone), cellulose, modifiedcellulose, carboxymethyl cellulose, hydroxyethyl cellulose,hydroxypropyl cellulose, methyl cellulose, hydrogels, PEG diacryalate,monoacrylate, and combinations thereof.

The low-surface-energy polymer and the hygroscopic material may becovalently connected in a block copolymer. In some embodiments, theblock copolymer includes a segmented copolymer composition comprising:

(a) one or more first soft segments selected from fluoropolymers havingan average molecular weight from about 500 g/mol to about 20,000 g/mol,wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated;

(b) optionally, one or more second soft segments selected frompolyesters or polyethers, wherein the polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated;

(c) one or more ionic species contained within the soft segments and/orcontained in copolymer chains that are distinct from the soft segments;

(d) one or more isocyanate species, or a reacted form thereof,possessing an isocyanate functionality of 2 or greater;

(e) one or more polyol or polyamine chain extenders or crosslinkers, ora reacted form thereof,

wherein the molar ratio of the second soft segments (if present) to thefirst soft segments is less than 2.0.

The fluoropolymers may include a fluoropolymer having the structure:

wherein:X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50;m=1 to 100; andn=1 to 100.

The coating optionally comprises one or more additional componentsselected from the group consisting of a particulate filler, a substrateadhesion promoter, a pigment, a dye, a plasticizer, a flattening agent,and a flame retardant. The particulate filler (when present) may beselected from the group consisting of silica, alumina, silicates, talc,aluminosilicates, barium sulfate, mica, diatomite, calcium carbonate,calcium sulfate, carbon, wollastonite, and combinations orsurface-treated derivatives thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the structure of some variations of the invention,providing an anti-fouling material.

FIG. 2 includes a table of experimental data of coating samples fromExamples A-F described herein.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The materials, compositions, structures, systems, and methods of thepresent invention will be described in detail by reference to variousnon-limiting embodiments.

This description will enable one skilled in the art to make and use theinvention, and it describes several embodiments, adaptations,variations, alternatives, and uses of the invention. These and otherembodiments, features, and advantages of the present invention willbecome more apparent to those skilled in the art when taken withreference to the following detailed description of the invention inconjunction with the accompanying drawings.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs.

Unless otherwise indicated, all numbers expressing conditions,concentrations, dimensions, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that may vary depending at least upona specific analytical technique.

The term “comprising,” which is synonymous with “including,”“containing,” or “characterized by” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps. “Comprising”is a term of art used in claim language which means that the named claimelements are essential, but other claim elements may be added and stillform a construct within the scope of the claim.

As used herein, the phase “consisting of” excludes any element, step, oringredient not specified in the claim. When the phrase “consists of” (orvariations thereof) appears in a clause of the body of a claim, ratherthan immediately following the preamble, it limits only the element setforth in that clause; other elements are not excluded from the claim asa whole. As used herein, the phase “consisting essentially of” limitsthe scope of a claim to the specified elements or method steps, plusthose that do not materially affect the basis and novelcharacteristic(s) of the claimed subject matter.

With respect to the terms “comprising,” “consisting of,” and “consistingessentially of,” where one of these three terms is used herein, thepresently disclosed and claimed subject matter may include the use ofeither of the other two terms. Thus in some embodiments not otherwiseexplicitly recited, any instance of “comprising” may be replaced by“consisting of” or, alternatively, by “consisting essentially of.”

Some variations of this invention are premised on the discovery of amaterial that possesses both low surface energy (for low adhesion) andthe ability to absorb water. A structured material or coating, asdisclosed, passively absorbs water from the atmosphere, to create alubrication/self-cleaning layer and reduce the friction and adhesion ofthe impacting body (such as an insect) on the surface. This anti-foulingmaterial may be used as a coating or as a surface.

U.S. patent application Ser. No. 14/658,188 (filed Mar. 14, 2015) andU.S. patent application Ser. No. 14/829,640 (filed Aug. 19, 2015), whichboth have a common assignee with the present application, are herebyincorporated by reference herein. These patent applications disclose,among other things, certain embodiments combining a fluorinatedperfluoropolyether (PFPE) as a low-surface-energy component andpolyethylene glycol (PEG) as a water-absorbing species in aurethane-based segmented copolymer. The present invention is predicatedon the incorporation of ionic species into or onto the polymer chainbackbone to increase the water-absorbing power (hygroscopic behavior) ofthe overall structure, beyond that of the PEG species alone. Improvementin lubrication or decrease in the coefficient of friction better enablesmaterial to be cleared from a surface using the natural motion of anautomotive or aerospace vehicle, for example. The present invention, insome variations, is premised on the incorporation of ionic species inthe coating to increase the amount of water naturally absorbed from theatmosphere and thus increase the lubrication, i.e. decrease thecoefficient of friction at the surface.

An anti-fouling coating in some embodiments may be characterized as“bugphobic,” which is intended to mean the coating has relatively lowadhesion with an impacting bug. Because these materials trap a layer ofwater near the surface, they also can delay the formation of ice, insome embodiments. An anti-fouling coating in some embodiments may becharacterized as “icephobic,” which is intended to mean the coating iscapable of delaying the formation of ice and/or causing a freezing-pointdepression of ice, compared to a bare substrate. The lubricatingcomponent has the ability to trap and organize a layer of water at thesurface to inhibit freezing.

The disclosed anti-fouling material can absorb water from the air anduse this water as a lubricant to wash and remove debris from thesurface. The surface contains domains of a low-surface-energy polymer(such as, but not limited to, a fluoropolymer) providing low adhesion,and domains of a hygroscopic material. The atmospheric water is thuscaptured as a lubricant and is a continually available, renewableresource.

By reducing friction, the debris is less likely to embed in or otherwiseattach to the surface and instead will tend to slough off the surface,particularly under the shear forces from air moving over a vehiclesurface. Debris may be organic or inorganic and may include insects,dirt, dust, soot, ash, pollutants, particulates, ice, seeds, plant oranimal fragments, plant or animal waste products, combinations orderivatives of any of the foregoing, and so on.

In some variations, anti-fouling structures are created by aheterogeneous microstructure comprising a low-surface-energy polymerthat is interspersed with hygroscopic domains (lubricating inclusions).Debris impacting the surface has low adhesion energy with the surface,due to the presence of the low-surface-energy polymer, and the debriswill not remain on the surface.

Preferred embodiments employ fluoropolymers, without limitation of theinvention, as described in more detail below. A preferred technique tocompatiblize fluoropolymers and hygroscopic materials is the use ofsegmented polyurethane or urea systems. These species demonstrate stronghydrogen bonding potential between them and as a result can createstrong associative forces between the chains. In order to produceelastomeric materials, regions of highly flexible and weakly interactingchains (soft segments) must be incorporated with strongly associatingelements (hard segments) and this can be provided in a segmentedcopolymerization scheme. Segmented copolymers provide a straightforwardsynthetic route toward block architectures using segments with vastlydiffering properties. Such synthesis results in chains that possessalternating hard and soft segments composed of regions of high urethanebond density and the chosen soft segment component (e.g., fluoropolymeror hygroscopic element), respectively. This covalent linkage ofdissimilar hard and soft blocks drives the systems to microphaseseparation and creates regions of flexible soft blocks surroundingregions of hard blocks. The associative forces among the hard segmentsprevent flow under stress and can produce elastomeric materials capableof displaying high elongation and tensile strength.

It has now been discovered that the hygroscopic or water-absorbingcharacter of the overall polymer film can be enhanced by the addition ofionic species as a hygroscopic soft segment component to complement thefluorinated soft segment, or as a separate soft segment in conjunctionwith other soft segments present. Due to their highly polar nature,ionic species have the ability to efficiently absorb water either whensubmerged in aqueous solution or naturally from the air in vapor form.

As used herein, an “ionic species” refers to ionized or ionizablemolecules which may be in the form of, or precursors to, anions,cations, or zwitterions. Ionic species may include (or be ionizable to)a full charge such as −1, −2, −3, +1, +2, +3, a fractional charge suchas −0.5, +0.5, −1.5 or +1.5, or a partial charge which in principle maybe any fraction of charge. “Ionizable” means that the molecule isneutral, i.e. net charge of 0, but capable of forming an anion, cation,or zwitterion; or that it is ionized but is capable of forming an anion,cation, or zwitterion having a larger magnitude of charge.

In some embodiments, the ionic species are high-molecular-weightpolyelectrolytes or polyelectrolyte precursors, some of which aredescribed in U.S. patent application Ser. No. 14/829,640, which has beenincorporated by reference above. A “polyelectrolyte” is defined as amacromolecule in which a substantial portion of the constitutional unitshave ionizable or ionic groups, or both.

Some embodiments incorporate small-molecule charged groups (i.e.,polymer pendant groups) along the chain backbone at various locations,depending on the order of addition. In these embodiments, the electricalcharge is typically present within the pendant group, not in the polymerbackbone itself.

In some embodiments, the ionic species are classified as ionomers. An“ionomer” is a polymer composed of ionomer molecules. An “ionomermolecule” is a macromolecule in which a small but significant proportionof the constitutional units have ionizable or ionic groups, or both.Some embodiments employ urethane-based ionomers capable of changingtheir crosslinked state under the influence of a change in counter ionvalance.

A zwitterion is a neutral molecule with a positive as well as a negativeelectrical charge. Multiple positive and negative charges may bepresent. Zwitterions are distinct from dipoles, at different locationswithin that molecule. Zwitterions are sometimes also called inner salts.Unlike simple amphoteric compounds that might only form either acationic or anionic species depending on external conditions, azwitterion simultaneously has both ionic states in the same molecule.

In addition to one or more ionic species, various counterions may bepresent, either intentionally or arising from external conditions. Acounterion may or may not be present; that is, there may be a net chargeassociated with the ionic species, or there may be charge neutrality ifa sufficient amount of counterions are ionically associated with theionic species. It is possible for there to be partial neutralization dueto counterions, so that the effective charge is something between theionic species charge and 0. It is also possible for there to be, atleast for some period of time, an excess of counterions so that theeffective charge is greater than the ionic species charge (i.e. morepositive or more negative when the ionic species is cationic or anionic,respectively).

Ionic constituents in polymers are both water-absorbing and typicallybound with counterions. When incorporated into polymer systems, ionicspecies have the ability to change the bulk and surface properties inresponse to materials bound to the network. These charged constituents,when incorporated into the polymer coating, can demonstrate reversibleinterchain cross-linking in some embodiments. Upon addition into thepolymer, the functional groups may be protonated and uncharged, allowingthe network to be held together by the hydrogen bonding in hard-segmentdomains of concentrated urethane bonds. To crosslink polymer films withmetal ions, films may be soaked in metal-containing solutions, such ascalcium hydroxide (Ca(OH)₂) solutions. Calcium ions are known to bindvery tightly to carboxylic acid groups where their divalent nature canact as a bridge between two monovalent carboxylate species to crosslinkchains into an overall network. The material may subsequently be soakedin an acidic solution, such as hydrochloric acid solutions, to protonatethe carboxylic acid groups for removal of Ca²⁺ ions, in reversiblecrosslinking.

An ionomer is a polymer that comprises repeat units of both electricallyneutral repeating units and a fraction of ionized units (usually no morethan 15 mole percent) covalently bonded to the polymer backbone aspendant group moieties. This means that ionomers are commonly copolymersof the neutral segments and the ionized units, which may consist of (asan example) carboxylic acid groups.

Ionomer synthesis may include the introduction of acid groups to thepolymer backbone and the neutralization of some of the acid groups by ametal cation. In some embodiments, the groups introduced are alreadyneutralized by a metal cation. The introduction of acid groups may beachieved by copolymerizing a neutral non-ionic monomer with a monomerthat contains pendant acid groups. Alternatively, acid groups may beadded to a non-ionic polymer through post-reaction modifications.Typically, the acid form of the copolymer is synthesized (i.e. all ofthe acid groups are neutralized by hydrogen cations) and the ionomer isformed through subsequent neutralization by a metal cation. The identityof the neutralizing metal cation has an effect on the physicalproperties of the ionomer. An acid copolymer may be melt-mixed with abasic metal or neutralization may be achieved through solutionprocesses.

The classification of a polymer as an ionomer versus polyelectrolyte(see below) depends on the level of substitution of ionic groups as wellas how the ionic groups are incorporated into the polymer structure. Forexample, polyelectrolytes also have ionic groups covalently bonded tothe polymer backbone, but have a higher ionic group molar substitutionlevel (usually greater than 80%).

Polyelectrolytes (charged molecular chains) are polymers whose repeatingunits bear an electrolyte group. Polycations and polyanions arepolyelectrolytes. These groups dissociate in aqueous solutions, makingthe polymers charged. Polyelectrolyte properties are thus similar toboth electrolytes (salts) and polymers and are sometimes calledpolysalts. Like salts, their solutions are electrically conductive. Likepolymers, their solutions are often viscous.

Polyelectrolytes can be divided into weak and strong types. A strongpolyelectrolyte is one which dissociates completely in solution for mostreasonable pH values. A weak polyelectrolyte, by contrast, has adissociation constant in the range of about 2 to 10, meaning that itwill be partially dissociated at intermediate pH. Thus, weakpolyelectrolytes are not fully charged in solution, and their fractionalcharge can be modified by changing the solution pH, counterionconcentration, or ionic strength.

A polyacid is a polyelectrolyte composed of macromolecules containingacid groups on a substantial fraction of the constitutional units. Forexample, the acid groups may be —COOH, —SO₃H, or —PO₃H₂.Polyelectrolytes which bear both cationic and anionic repeat groups arecalled polyampholytes.

In some embodiments of the invention, the ionic species include two ormore reactive groups such as alcohol or amine moieties. Specific exampleinclude, but are not limited to, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalcium salt, 2,2-bis-(1-(1-methylimidazolium)-methylpropane-1,3-diol bromide),1,2-bis-(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, dimethylolpropionic acid, N-methyldiethanolamine,N-ethyldiethanolamine, N-propyldiethanolamine, N-benzyldiethanolamine,N-t-butyldiethanolamine, bis(2-hydroxyethyl) benzylamine, andbis(2-hydroxypropyl) aniline.

Partial atomic charges can be used to quantify the degree of ionicversus covalent bonding of any particular compound that is selected as,or may be a candidate for, an ionic species. Partial charges for a givenionic species can be estimated in multiple ways, such as: densities;measured dipole moments; the Extended Born thermodynamic cycle,including an analysis of ionic bonding contributions; the influence ofcoordination numbers and aggregate state of a given compound on atomiccharges; the relationship of atomic charges to melting points,solubility, and cleavage energies for a set of similar compounds withsimilar degree of covalent bonding; the relationship of atomic chargesto chemical reactivity and reaction mechanisms for similar compounds; orthe relationship between chemical structure and atomic charges forcomparable compounds with known atomic charges.

Partial charges in ionic species may be determined by populationanalysis of wavefunctions (e.g., Mulliken population analysis, Coulson'scharges, etc.); partitioning of electron density distributions (e.g.,Bader charges, Hirshfeld charges, Politzer's charges, etc.); chargesderived from dipole-dependent properties (e.g., dipole charges, dipolederivative charges, Born, Callen, or Szigeti effective charges, etc.);charges derived from electrostatic potential (e.g., Chelp,Merz-Singh-Kollman, etc.); charges derived from spectroscopic data(e.g., charges from infrared intensities, X-ray photoelectronspectroscopy, X-ray emission spectroscopy, X-ray absorption spectra,UV-vis intensities of transition metal complexes, etc.); charges fromother experimental data (e.g., charges from bandgaps or dielectricconstants, apparent charges from the piezoelectric effect, chargesderived from adiabatic potential energy curves, orelectronegativity-based charges), or formal charges.

In a specific embodiment, there is provided a segmented copolymercomposition. The composition comprises one or more α,ω(alpha,omega)-amine-terminated or α,ω(alpha, omega)-hydroxyl-terminatedpolyfluoropolymer first soft segments having an average molecular weightof between about 500 grams per mole to about 20,000 grams per mole. Theexemplary composition further comprises one or more polyethylene glycolsecond soft segments having an average molecular weight of between about500 grams per mole to about 20,000 grams per mole. Additionally, thecomposition may comprise one or more low-molecular-weight chargedmonomer species. A total content of the one or more first soft segmentsand the one or more second soft segments is from about 40% by weight toabout 90% by weight, based on a total weight percent of the composition.The composition further comprises one or more hard segments present, forexample, in an amount of from about 15% by weight to about 50% byweight, based on the total weight percent of the composition. The one ormore hard segments comprise a combination of one or more isocyanatespecies and one or more low-molecular-weight polyol or polyamine chainextenders or crosslinkers.

Some variations provide a segmented copolymer composition comprising:

(a) one or more first soft segments selected from fluoropolymers havingan average molecular weight from about 500 g/mol to about 20,000 g/mol,wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated;

(b) optionally, one or more second soft segments selected frompolyesters or polyethers, wherein the polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated;

(c) one or more ionic species contained within the soft segments and/orcontained in copolymer chains that are distinct from the soft segments;

(d) one or more isocyanate species, or a reacted form thereof,possessing an isocyanate functionality of 2 or greater; and

(e) one or more polyol or polyamine chain extenders or crosslinkers, ora reacted form thereof.

It is noted that (α,ω)-terminated polymers are terminated at each end ofthe polymer. The α-termination may be the same or different than theco-termination. Also it is noted that in this disclosure,“(α,ω)-termination” includes branching at the ends, so that the numberof terminations may be greater than 2 per polymer molecule. The polymersherein may be linear or branched, and there may be various terminationsand functional groups within the polymer chain, besides the end (α,ω)terminations.

In some embodiments, the molar ratio of the second soft segments (whenpresent) to the first soft segments is from about 0.1 to about 2.0. Invarious embodiments, the molar ratio of the second soft segments to thefirst soft segments is about 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 1.95.

In this description, “polyurethane” is a polymer comprising a chain oforganic units joined by carbamate (urethane) links, where “urethane”refers to N(H)—(C═O)—O—. Polyurethanes are generally produced byreacting an isocyanate containing two or more isocyanate groups permolecule with one or more polyols containing on average two or morehydroxyl groups per molecule, in the presence of a catalyst.

Polyols are polymers in their own right and have on average two or morehydroxyl groups per molecule. For example, α,ω-hydroxyl-terminatedperfluoropolyether is a type of polyol.

“Isocyanate” is the functional group with the formula —N═C═O. For thepurposes of this disclosure, S—C(═O)—N(H)—R is considered a derivativeof isocyanate.

“Polyfluoroether” refers to a class of polymers that contain an ethergroup—an oxygen atom connected to two alkyl or aryl groups, where atleast one hydrogen atom is replaced by a fluorine atom in an alkyl oraryl group.

“Perfluoropolyether” (PFPE) is a highly fluorinated subset ofpolyfluoroethers, wherein all hydrogen atoms are replaced by fluorineatoms in the alkyl or aryl groups.

“Polyurea” is a polymer comprising a chain of organic units joined byurea links, where “urea” refers to N(H)—(C═O)—N(H)—. Polyureas aregenerally produced by reacting an isocyanate containing two or moreisocyanate groups per molecule with one or more multifunctional amines(e.g., diamines) containing on average two or more amine groups permolecule, in the presence of a catalyst.

A “chain extender or crosslinker” is a compound (or mixture ofcompounds) that link long molecules together and thereby complete apolymer reaction. Chain extenders or crosslinkers are also known ascuring agents, curatives, or hardeners. In polyurethane/urea systems, acurative is typically comprised of hydroxyl-terminated oramine-terminated compounds which react with isocyanate groups present inthe mixture. Diols as curatives form urethane linkages, while diaminesas curatives form urea linkages. The choice of chain extender orcrosslinker may be determined by end groups present on a givenprepolymer. In the case of isocyanate end groups, curing can beaccomplished through chain extension using multifunctional amines oralcohols, for example. Chain extenders or crosslinkers can have anaverage functionality greater than 2 (such as 3 or greater), i.e. beyonddiols or diamines.

The one or more chain extenders or crosslinkers (or reaction productsthereof) may be present in a concentration, in the segmented copolymercomposition, from about 0.01 wt % to about 10 wt %, such as about 0.05wt % to about 1 wt %.

As meant herein, a “low-surface-energy polymer” means a polymer, or apolymer-containing material, with a surface energy of no greater than 50mJ/m². The principles of the invention may be applied tolow-surface-energy materials with a surface energy of no greater than 50mJ/m², in general (i.e., not necessarily limited to polymers).

In some embodiments, the low-surface-energy polymer includes afluoropolymer, such as (but not limited to) a fluoropolymer selectedfrom the group consisting of polyfluoroethers, perfluoropolyethers,fluoroacrylates, fluorosilicones, and combinations thereof.

In these or other embodiments, the low-surface-energy polymer includes asiloxane. A siloxane contains at least one Si—O—Si linkage. Thelow-surface-energy polymer may consist of polymerized siloxanes orpolysiloxanes (also known as silicones). One example ispolydimethylsiloxane.

In some embodiments, the fluoropolymers are selected from the groupconsisting of perfluoropolyethers, polyfluoroacrylates,polyfluorosiloxanes, and combinations thereof. In certain embodiments,the fluoropolymers include a fluoropolymer copolymer with poly(ethyleneglycol) having the formulaHO—(CH₂—CH₂—O)_(p)—CH₂—CF₂—O—(CF₂—CF₂—O)_(m)(CF₂—O)_(n)—CF₂—CH₂—(O—CH₂—CH₂)_(p)—OH(p=0 to 50; m=1 to 100; and n=1 to 100), with the following structure:

wherein:X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50;m=1 to 100; andn=1 to 100.

In certain embodiments, the chain ends include different PEG chainlengths. That is, the fluoropolymers may include a fluoropolymersegmented copolymer with poly(ethylene glycol) having the formulaHO—(CH₂—CH₂-0)_(p)—CH₂—CF₂—O—(CF₂—CF₂—O)_(m)(CF₂—O)_(n)—CF₂—CH₂—(O—CH₂—CH₂)_(q)—OHwherein p=0 to 50; q=0 to 50 and q is independently selected from p; m=1to 100; and n=1 to 100. In certain of these embodiments, one of either por q is selected from 6 to 50 while the other is selected from 0 to 50.In some embodiments, one or both of the X groups is amine-terminatedrather than hydroxyl-terminated.

In some embodiments, the polyesters or polyethers are selected from thegroup consisting of poly(oxymethylene), poly(ethylene glycol),poly(propylene glycol), poly(tetrahydrofuran), poly(glycolic acid),poly(caprolactone), poly(ethylene adipate), poly(hydroxybutyrate),poly(hydroxyalkanoate), and combinations thereof.

In some embodiments, the isocyanate species is selected from the groupconsisting of 4,4′-methylenebis(cyclohexyl isocyanate), hexamethylenediisocyanate, cycloalkyl-based diisocyanates, tolylene-2,4-diisocyanate,4,4′-methylenebis(phenyl isocyanate), isophorone diisocyanate, andcombinations or derivatives thereof.

The polyol or polyamine chain extender possesses a functionality of 2 orgreater, in some embodiments. At least one polyol or polyamine chainextender may be selected from the group consisting of 1,4-butanediol,1,3-propanediol, 1,2-ethanediol, glycerol, trimethylolpropane,ethylenediamine, isophoronediamine, diaminocyclohexane, and homologues,derivatives, or combinations thereof.

Following a suitable chemical reaction, the segmented copolymercomposition contains, in a hard segment, the reacted form of the one ormore isocyanate species, combined with the reacted form of the one ormore polyol or polyamine chain extenders or crosslinkers. In someembodiments, the hard segment is present in an amount from about 5 wt %to about 60 wt %, based on total weight of the composition.

The segmented copolymer composition may be present in a coating, forexample. Such a coating may be characterized by a contact angle of wateron a coating surface of greater than 90°. Such a coating may becharacterized by an average kinetic delay of surface ice formation of atleast 5 minutes at −10° C.

The structure of some variations of the invention is shown in FIG. 1.FIG. 1 depicts the structure of a coating or surface with anti-foulingproperties.

The structure 100 of FIG. 1 includes a continuous matrix 110. A“continuous matrix” (or equivalently, “substantially continuous matrix”)means that the matrix material is present in a form that includeschemical bonds among molecules of the matrix material. An example ofsuch chemical bonds is crosslinking bonds between polymer chains. Thestructure 100 further includes a plurality of inclusions 120, dispersedwithin the matrix 110, each of the inclusions 120 comprising ahygroscopic material containing one or more ionic species. In certainembodiments, the hygroscopic material is fabricated from ionomers,polyelectrolytes, and/or other ionic species described above. Note thatthe functions of the matrix and inclusions may be reversed, such thatthe matrix provides hygroscopic properties while the inclusions providelow surface energy.

Optionally, the continuous matrix 110 may further comprise one or moreadditives selected from the group consisting of fillers, colorants, UVabsorbers, defoamers, plasticizers, viscosity modifiers, densitymodifiers, catalysts, and scavengers. In a substantially continuousmatrix 110, there may be present various defects, cracks, broken bonds,impurities, additives, and so on.

Some variations provide an anti-fouling material (e.g., coating or bulkmaterial) comprising:

a substantially continuous matrix containing a first component;

a plurality of inclusions containing a second component, wherein theinclusions are dispersed within the matrix;

wherein one of the first component or the second component is alow-surface-energy polymer having a surface energy between about 5 mJ/m²to about 50 mJ/m², and the other of the first component or the secondcomponent is a hygroscopic material containing one or more ionicspecies,

wherein the low-surface-energy polymer and the hygroscopic material arechemically connected ionically or covalently,

and wherein the continuous matrix and the inclusions form a lubricatingsurface layer in the presence of humidity.

In some embodiments, the surface energy of the low-surface-energypolymer is between about 10 mJ/m² to about 40 mJ/m², such as about 10,15, 20, 25, 30, 35, or 40, mJ/m². In some preferred embodiments, thelow-surface-energy polymer is a fluoropolymer selected from the groupconsisting of polyfluoroethers, perfluoropolyethers,polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.

The hygroscopic material may include a material selected from the groupconsisting of 2,2-bis-(1-(1-methyl imidazolium)-methylpropane-1,3-diolbromide), 1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl) butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.

The hygroscopic material may include a material selected from the groupconsisting of poly(acrylic acid), poly(ethylene glycol),poly(2-hydroxyethyl methacrylate), poly(vinyl imidazole),poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline),poly(vinylpyrolidone), cellulose, modified cellulose, carboxymethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose, hydrogels, PEG diacryalate, monoacrylate, and combinationsthereof. When the hygroscopic material includes one or more of thematerials from this list, the hygroscopic material may further includeone or more ionic species selected from the group consisting of2,2-bis-(1-(1-methyl imidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.

The low-surface-energy polymer and the hygroscopic material may bephase-separated, i.e. they do not form a single continuous phase. Thereis preferably chemical and/or physical bonding between thelow-surface-energy polymer and the hygroscopic material.

In some embodiments, the inclusions are three-dimensional objects ordomains, which may be of any shape, geometry, or aspect ratio. In athree-dimensional object, an aspect ratio of exactly 1.0 means that allthree characteristic length scales are identical, such as in a perfectcube. The aspect ratio of a perfect sphere is also 1.0. The inclusionsmay be geometrically symmetric or asymmetric. Randomly shaped asymmetrictemplates are, generally speaking, geometrically asymmetric. In someembodiments, inclusions are geometrically symmetric. Examples includecylinders, cones, rectangular prisms, pyramids, or three-dimensionalstars.

In some embodiments, the inclusions are anisotropic. As meant herein,“anisotropic” inclusions have at least one chemical or physical propertythat is directionally dependent. When measured along different axes, ananisotropic inclusion will have some variation in a measurable property.The property may be physical (e.g., geometrical) or chemical in nature,or both.

The inclusions may be characterized as templates, domains, or regions(such as phase-separated regions). The inclusions are not a single,continuous framework in the coating. Rather, the inclusions arediscrete, non-continuous and dispersed in the continuous matrix. Thehygroscopic inclusions may be dispersed uniformly within the continuousmatrix. In some anti-fouling materials, the low-surface-energy polymerand the hygroscopic material are covalently connected in a blockcopolymer, in which the inclusions and the continuous matrix aredistinct phases of the block copolymer.

As intended herein, a “block copolymer” means a copolymer containing alinear arrangement of blocks, where each block is defined as a portionof a polymer molecule in which the monomeric units have at least oneconstitutional or configurational feature absent from the adjacentportions. Several types of block copolymers are generally possible,including AB block copolymers, ABA block copolymers, ABC blockcopolymers, segmented block copolymers, and random copolymers. Segmentedblock copolymers are preferred, in some embodiments of the invention.

For example, a block copolymer may be a segmented copolymer compositioncomprising:

(a) one or more first soft segments selected from fluoropolymers havingan average molecular weight from about 500 g/mol to about 20,000 g/mol,wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated;

(b) optionally, one or more second soft segments selected frompolyesters or polyethers, wherein the polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated;

(c) one or more ionic species contained within the soft segments and/orcontained in copolymer chains that are distinct from the soft segments;

(d) one or more isocyanate species, or a reacted form thereof,possessing an isocyanate functionality of 2 or greater; and

(e) one or more polyol or polyamine chain extenders or crosslinkers, ora reacted form thereof.

In some embodiments, the fluoropolymers include a fluoropolymer havingthe structure:

wherein:X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50;m=1 to 100; andn=1 to 100.

In some embodiments, the polyesters or polyethers are selected from thegroup consisting of poly(oxymethylene), poly(ethylene glycol),poly(propylene glycol), poly(tetrahydrofuran), poly(glycolic acid),poly(caprolactone), poly(ethylene adipate), poly(hydroxybutyrate),poly(hydroxyalkanoate), and combinations thereof.

In some embodiments, the molar ratio of the second soft segments to thefirst soft segments is less than 2.0, such as from about 0.1 to about1.5.

A wide range of concentrations of components may be present in theanti-fouling material. For example, the continuous matrix may be fromabout 5 wt % to about 95 wt %, such as from about 10 wt % to about 50 wt% of the material. The inclusions may be from about 1 wt % to about 90wt %, such as from about 10 wt % to about 50 wt % of the coating.

Within the component containing the low-surface-energy polymer, thelow-surface-energy polymer may be from about 50 wt % to 100 wt %, suchas about 60, 70, 80, 90, 95, or 100 wt %. Within the componentcontaining the hygroscopic material, the hygroscopic material may befrom about 50 wt % to 100 wt %, such as about 60, 70, 80, 90, 95, or 100wt %.

The low-surface-energy polymer and/or the hygroscopic material may besurface-treated, such as to adjust hydrophobicity. The anti-foulingmaterial optionally further contains one or more additional componentsselected from the group consisting of a particulate filler, a pigment, adye, a plasticizer, a flame retardant, a flattening agent, and asubstrate adhesion promoter.

A particulate filler may be selected from the group consisting ofsilica, alumina, silicates, talc, aluminosilicates, barium sulfate,mica, diatomite, calcium carbonate, calcium sulfate, carbon,wollastonite, and combinations thereof. The particulate fillersgenerally should be in the size range of about 5 nm to about 2 μm, suchas about 20 nm to 100 nm.

The particulate fillers may be surface-modified with a compound selectedfrom the group consisting of fatty acids, silanes, silicones, alkylphosphonates, alkyl phosphonic acids, alkyl carboxylates, andcombinations thereof. Optionally, the fillers may be surface-modifiedwith a hydrophobic material, such as (but not limited to) analkylsilane, a fluoroalkylsilane, and/or an alkyldisilazane (e.g.,hexamethyldisilazane).

In some embodiments, the anti-fouling material further includes voids.As intended herein, a “void” is a discrete region of empty space, orspace filled with air or another gas, that is enclosed within thecontinuous matrix. The voids may be open (e.g., interconnected voids) orclosed (isolated within the continuous matrix), or a combinationthereof. The voids may partially surround inclusions.

The domains of hygroscopic material exist throughout the material, inboth planar and depth dimensions. The anti-fouling function is retainedeven after some sort of abrasion of the top layer of the material.

Some compositions include both a polyether and an aliphatic diolcarrying an acid group as part of the composition, but does not includealiphatic diols containing long carbon chains having >10 carbons. Someembodiments do not incorporate polyols containing three or more reactivehydroxyl groups. Some compositions contain ionizable groups incombination with perfluoropolyethers, but do not incorporate silanes forcrosslinking. Preferred embodiments do not incorporate waterbornepolyurethanes with charged groups to create stable colloidal dispersionsin water.

The coefficient of friction of the anti-fouling material is relativelylow due to the presence of a lubricating surface layer in the presenceof humidity. By a “lubricating surface layer in the presence ofhumidity,” it is meant a layer, multiple layers, a partial layer, or anamount of substance that lubricates the substrate such that it has alower coefficient of friction compared to the substrate without thematerial present, when in the presence of some amount of atmospherichumidity.

The specific level of humidity is not regarded as critical, but ingeneral may range from about 1% to 100%, typically about 30% to about70% relative humidity. Relative humidity is the ratio of the water vapordensity (mass per unit volume) to the saturation water vapor density.Relative humidity is approximately the ratio of the actual partialpressure of water vapor to the saturation (maximum) vapor pressure ofwater in air.

The substance that lubricates the substrate is primarily water, but itshould be noted that other components from the environment may bepresent in the lubricating surface layer, including oils, metals, dust,dissolved gases, dissolved aqueous components, suspended non-aqueouscomponents, fragments of debris, fragments of polymers, and so on.

In some embodiments, the anti-fouling material is characterized by acoefficient of friction, measured at 40-55% (e.g. 50%) relative humidityand room temperature, less than 0.5, 0.4, 0.3, 0.2, 0.15 or less. Inthese or other embodiments, the anti-fouling material is characterizedby a coefficient of friction, measured at 85-90% relative humidity androom temperature, less than 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.15, orless.

The anti-fouling material may be characterized by a surface contactangle of water of greater than 90° (hydrophobic). In variousembodiments, the material is characterized by an effective contact angleof water of about 80°, 85°, 90°, 95°, 100°, 105°, 110°, or higher. Thematerial may also be hydrophilic, i.e. characterized by an effectivecontact angle of water that is less than 90°.

The material may also be lipophobic or partially lipophobic in someembodiments. In various embodiments, the anti-fouling material ischaracterized by an effective contact angle of hexadecane (as a measureof lipophobicity) of about 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°,or higher.

The anti-fouling material may simultaneously have hydrophobic andlipophobic properties. In certain embodiments, the material ischaracterized by an effective contact angle of water of at least 90°(such as about 95-110°) and simultaneously an effective contact angle ofhexadecane of at least 60° (such as about) 65°. In certain embodiments,the material is characterized by an effective contact angle of water ofat least 80° (such as about 80-85°) and simultaneously an effectivecontact angle of hexadecane of at least 70° (such as about 75-80°).

The anti-fouling material may be characterized by a water absorptioncapacity of at least 10 wt % water based on total weight of theanti-fouling material. The material is characterized, according to someembodiments, by a water absorption capacity of at least 1, 2, 3, 4, 5,6, 7, 8, or 9 wt % water, preferably at least 10, 11, 12, 13, 14, 15,16, 17, 18, 19, or 20 wt % water, based on total weight of the material.

The anti-fouling material may be characterized by a delay in theformation of ice on a surface of the material. For example, when ananti-fouling material surface is held at −10° C., the material providedby the invention may be characterized by an average delay in theformation of ice on the surface of at least about 10, 15, 20, 25, 30minutes, or more.

In various embodiments, the anti-fouling material is a coating and/or ispresent at a surface of an object or region. The material may beutilized in relatively small applications, such as lens coatings, or forlarge structures, such as aircraft wings. In principle, the materialcould be present within a bulk region of an object or part, or couldcontain a temporary, protective laminating film for storage ortransport, which is later removed to adhere to the vehicle, for example.

Variations of the invention also provide a precursor material for ananti-fouling material, the precursor material comprising:

a hardenable material capable of forming a substantially continuousmatrix containing a first component; and

a plurality of inclusions containing a second component, wherein theinclusions are dispersed within the hardenable material,

wherein one of the first component or the second component is alow-surface-energy polymer having a surface energy between about 5 mJ/m²to about 50 mJ/m², and the other of the first component or the secondcomponent is a hygroscopic material containing one or more ionicspecies,

and wherein the low-surface-energy polymer and the hygroscopic materialare chemically connected ionically or covalently.

In some embodiments, the surface energy of the low-surface-energypolymer is between about 10 mJ/m² to about 40 mJ/m², such as about 10,15, 20, 25, 30, 35, or 40, mJ/m². In some embodiments, thelow-surface-energy polymer is a fluoropolymer, such as one selected fromthe group consisting of polyfluoroethers, perfluoropolyethers,polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof.

In some embodiments, the hygroscopic material in the precursor materialis selected from the group consisting of poly(acrylic acid),poly(ethylene glycol), poly(2-hydroxyethyl methacrylate), poly(vinylimidazole), poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline),poly(vinylpyrolidone), cellulose, modified cellulose, carboxymethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose, hydrogels, PEG diacryalate, monoacrylate, and combinationsthereof. Alternatively, or additionally, the hygroscopic material maycomprise one or more ionic species selected from the group consisting of2,2-bis-(1-(1-methyl imidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.

The low-surface-energy polymer and the hygroscopic material may becovalently connected, or are capable of being covalently connected, in ablock copolymer. For example, a block copolymer (in the precursormaterial) may be a segmented copolymer composition comprising:

(a) one or more first soft segments selected from fluoropolymers havingan average molecular weight from about 500 g/mol to about 20,000 g/mol,wherein the fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated;

(b) optionally, one or more second soft segments selected frompolyesters or polyethers, wherein the polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated;

(c) one or more ionic species contained within the soft segments and/orcontained in copolymer chains that are distinct from the soft segments;

(d) one or more isocyanate species, or a reacted form thereof,possessing an isocyanate functionality of 2 or greater; and

(e) one or more polyol or polyamine chain extenders or crosslinkers, ora reacted form thereof.

In some embodiments, the fluoropolymers include a fluoropolymer havingthe structure:

wherein:X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50;m=1 to 100; andn=1 to 100.

The low-surface-energy polymer and/or the hygroscopic material may besurface-treated, either prior to introduction into the precursormaterial or prior to conversion of the precursor material to theanti-fouling material.

The precursor material may further contain one or more additionalcomponents selected from the group consisting of a particulate filler, apigment, a dye, a plasticizer, a flame retardant, a flattening agent,and a substrate adhesion promoter. Alternatively, or additionally, suchadditional components may be introduced during the conversion of theprecursor material to the anti-fouling material, or to the anti-foulingmaterial after it is formed.

Specific particulate fillers include, for example, silica, alumina,silicates, talc, aluminosilicates, barium sulfate, mica, diatomite,calcium carbonate, calcium sulfate, carbon, wollastonite, andcombinations thereof. The particulate fillers generally should be in thesize range of about 5 nm to about 2 μm, such as about 20 nm to 100 nm.

The particulate fillers may be surface-modified with a compound selectedfrom the group consisting of fatty acids, silanes, silicones, alkylphosphonates, alkyl phosphonic acids, alkyl carboxylates, andcombinations thereof. Optionally, the fillers may be surface-modifiedwith a hydrophobic material, such as (but not limited to) analkylsilane, a fluoroalkylsilane, and/or an alkyldisilazane (e.g.,hexamethyldisilazane).

Any known methods to fabricate these materials or coatings may beemployed. Notably, these materials or coatings may utilize synthesismethods that enable simultaneous deposition of components or precursormaterials to reduce fabrication cost and time. In particular, thesematerials or coatings may be formed by a one-step process, in someembodiments. In other embodiments, these materials or coatings may beformed by a multiple-step process. Preferred coatings are cast orsprayed from organic solution rather than aqueous solution.

The anti-fouling hydrophobic or hydrophilic material, in someembodiments, is formed from a precursor material (or combination ofmaterials) that may be provided, obtained, or fabricated from startingcomponents. The precursor material is capable of hardening or curing insome fashion, to form a substantially continuous matrix along with aplurality of inclusions, dispersed within the matrix. The precursormaterial may be a liquid; a multiphase liquid; a multiphase slurry,emulsion, or suspension; a gel; or a dissolved solid (in solvent), forexample.

The low-surface-energy polymer and the hygroscopic material may be inthe same phase or in different phases. In some embodiments, thelow-surface-energy polymer is in liquid or dissolved form while thehygroscopic material is in dissolved-solid or suspended solid form. Insome embodiments, the low-surface-energy polymer is dissolved-solid orsuspended-solid form while the hygroscopic material is in liquid ordissolved form. In some embodiments, the low-surface-energy polymer andthe hygroscopic material are both in liquid form. In some embodiments,the low-surface-energy polymer and the hygroscopic material are both indissolved (solvent) form.

Some embodiments employ one-shot polymerization to produce a copolymer.In one-shot polymerization, the reactants (e.g., fluoropolymer,isocyanate species, and polyol or polyamine chain extenders orcrosslinkers) are mixed together in the liquid phase in a suitablecontainer, within a mold, or on a substrate, and allowed to reactsimultaneously. No prepolymer is first formed.

In some variations of the invention, a material or coating precursor isapplied to a substrate (such as a surface of an automobile or aircraft)and allowed to react, cure, or harden to form a final coating, whereinthe material, coating precursor, or final coating contains a segmentedcopolymer composition as disclosed herein.

In some embodiments, the hygroscopic material is also hardenable, eitheralone or in combination with the low-surface-energy polymer. Forinstance, a low-surface-energy polymer and a hygroscopic polymer mayform a high-molecular-weight block copolymerize and thus harden. Incertain embodiments, the hygroscopic material assists in the curability(hardenability) of the low-surface-energy polymer.

In some embodiments, a precursor material is prepared and then dispensed(deposited) over an area of interest. Any known methods to depositprecursor materials may be employed. A fluid precursor material allowsfor convenient dispensing using spray coating or casting techniques overa large area, such as the scale of a vehicle or aircraft.

The fluid precursor material may be applied to a surface using anycoating technique, such as (but not limited to) spray coating, dipcoating, doctor-blade coating, spin coating, air knife coating, curtaincoating, single and multilayer slide coating, gap coating,knife-over-roll coating, metering rod (Meyer bar) coating, reverse rollcoating, rotary screen coating, extrusion coating, casting, or printing.Because relatively simple coating processes may be employed, rather thanlithography or vacuum-based techniques, the fluid precursor material maybe rapidly sprayed or cast in thin layers over large areas (such asmultiple square meters).

When a solvent or carrier fluid is present in the fluid precursormaterial, the solvent or carrier fluid may include one or more compoundsselected from the group consisting of water, alcohols (such as methanol,ethanol, isopropanol, or tert-butanol), ketones (such as acetone, methylethyl ketone, or methyl isobutyl ketone), hydrocarbons (e.g., toluene),acetates (such as tert-butyl acetate), acids (such as organic acids),bases, and any mixtures thereof. When a solvent or carrier fluid ispresent, it may be in a concentration of from about 10 wt % to about 99wt % or higher, for example.

The precursor material may be converted to an intermediate material orthe final material using any one or more of curing or other chemicalreactions, or separations such as removal of solvent or carrier fluid,monomer, water, or vapor. Curing refers to toughening or hardening of apolymeric material by cross-linking of polymer chains, assisted byelectromagnetic waves, electron beams, heat, and/or chemical additives.Chemical removal may be accomplished by heating/flashing, vacuumextraction, solvent extraction, centrifugation, etc. Physicaltransformations may also be involved to transfer precursor material intoa mold, for example. Additives may be introduced during the hardeningprocess, if desired, to adjust pH, stability, density, viscosity, color,or other properties, for functional, ornamental, safety, or otherreasons.

The overall thickness of the final material or coating may be from about1 μm to about 1 cm or more, such as about 10 μm, 20 μm, 25 μm, 30 μm, 40μm, 50 μm, 75 μm, 100 μm, 500 μm, 1 mm, 1 cm, or 10 cm. Relatively thickcoatings offer good durability and mechanical properties, such as impactresistance, while preferably being relatively lightweight.

EXAMPLES

Materials.

Poly(ethylene glycol) (PEG) with molecular weight (M_(n)) of 3,400g/mol, 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI), 1,4-butanediol(BD), dibutyltin dilaurate (DBTDL), and 2,2-bis(hydroxymethyl)propionicacid are purchased from Aldrich. Fluorolink materials are purchased fromSolvay Specialty Polymers. All chemicals are used as received withoutfurther purification.

Example A: Fluoropolymer Control

Fluorolink D4000 perfluoropolyether (4 g) is charged to a vial followedby HMDI (0.786 g) and dibutyltin dilaurate (0.02%). A small PTFE-coatedstir bar is introduced and the vial is placed in a 100° C. oil bath tostir. The reaction is vortexed aggressively after achieving atemperature of 100° C., and then left to stir for 1 hour. After thisstep, the resin is poured into a 3″×3″ PTFE mold to flash off solventand cure the film at room temperature overnight.

Example B: Thermoplastic Polymer without Ionic Species

Hydroxyl-terminated poly(perfluoropolyether) (9.00 g, 3.73 mmol,Fluorolink 5147x) is placed in a 3-neck roundbottom flask that containsan inlet for argon and equipped with an overhead stirrer (Teflon shaftand blade). While stirring, 4,4′-methylenebis(cyclohexyl isocyanate)(4.89 g, 18.66 mmol) is added to the solution and the flask is placed inan oil bath at 100° C. Dibutyltin dilaurate (0.02 wt %) is then added tothe solution using a micropipette and the polymerization reaction isallowed to proceed.

After 1 hr, the prepolymer is then allowed to cool down to roomtemperature. The prepolymer is diluted with tetrahydrofuran (15 mL) andplaced in a centrifugal mixer (FlackTek DAC 600).

In a separate vial, chain extender 1,4-butanediol (1.35 g, 14.98 mmol)is weighed and diluted with tetrahydrofuran (0.5 mL). The two solutionsare combined in a centrifugal mixer and mixed at 2300 rpm for 15seconds. The polymer is cast from solution or sprayed using an airbrushto create a polyurethane film/coating.

Example C: Thermoplastic Polymer with Ionic Species

Hydroxyl-terminated poly(perfluoropolyether) (9.00 g, 3.73 mmol,Fluorolink 5147x) is placed in a 3-neck roundbottom flask that containsan inlet for argon and equipped with an overhead stirrer (Teflon shaftand blade). While stirring, 4,4′-methylenebis(cyclohexyl isocyanate)(4.89 g, 18.66 mmol) is added to the solution and the flask is placed inan oil bath at 100° C. Dibutyltin dilaurate (0.02 wt %) catalyst is thenadded to the solution using a micropipette and the polymerizationreaction is allowed to proceed.

After 1 hr, the ionic species precursor 2,2-bis(hydroxymethyl)propionicacid (0.50 g, 3.74 mmol) is added to the stirring solution and allowedto dissolve and react for 1 hr. The prepolymer is then allowed to cooldown to room temperature. The prepolymer is diluted with tetrahydrofuran(15 mL) and placed in a plastic mixing container for centrifugal mixing.

In a separate vial, chain extender 1,4-butanediol (1.01 g, 11.21 mmol)is weighed and diluted with tetrahydrofuran (0.5 mL). The two solutionsare combined in mixing centrifugal mixer and mixed at 2300 rpm for 15seconds to form polymer. The polymer is cast from solution or sprayedusing an airbrush to create a polyurethane film/coating.

Multiple samples are prepared, as follows. Sample C1 is unsoaked, sampleC2 is soaked in deionizied water, sample C3 is soaked in 0.01 M HCl, andsample C4 is soaked in 0.01 M Ca(OH)₂. Samples C1, C2, C3, and C4 arethen tested in accordance with Example F (friction testing) below.

Example D: High-Molecular Weight PEG Combined with PFPE/PEG Triblockwithout Ionic Species

Hydroxyl-terminated poly(ethylene glycol) (M_(n)=3400, 2.50 g, 0.74mmol) is placed in a 3-neck roundbottom flask that contains an inlet forargon and equipped with an overhead stirrer (Teflon shaft and blade).While stirring, 4,4′-methylenebis(cyclohexyl isocyanate) (3.72 g, 14.20mmol) is added to the solution and the flask is placed in an oil bath at100° C. Dibutyltin dilaurate (0.02 wt %) is then added to the solutionusing a micropipette and the polymerization reaction is allowed toproceed.

After 1 hr, Fluorolink E10-H (2.78 g, 1.40 mmol) is added to thestirring solution and allowed to react for 2 hr at 100° C. Theprepolymer is then allowed to cool down to room temperature. Theprepolymer is diluted with tetrahydrofuran (9.15 mL) and placed in aplastic mixing cup before inserting into the centrifugal mixer.

In a separate vial, 1,4-butanediol (0.77 g, 8.54 mmol) is weighed anddiluted with tetrahydrofuran (0.5 mL). The two solutions are combined ina centrifugal mixer and mixed at 2300 rpm for 15 seconds. The polymer iscast from solution or sprayed using an airbrush to create a polyurethanefilm/coating.

Multiple samples are prepared, as follows. Sample D1 is unsoaked, sampleD2 is soaked in deionizied water, and sample D3 is soaked in NaOH atpH=14. Samples D1, D2, and D3 are then tested in accordance with ExampleF (friction testing) below.

Example E: High-Molecular Weight PEG Combined with PFPE/PEG Triblockwith Ionic Species

Hydroxyl-terminated poly(ethylene glycol) (2.50 g, 0.74 mmol) is placedin a 3-neck roundbottom flask that contains an inlet for argon andequipped with an overhead stirrer (Teflon shaft and blade). Whilestirring, 4,4′-methylenebis(cyclohexyl isocyanate) (4.49 g, 17.14 mmol)is added to the solution and the flask is placed in an oil bath at 100°C. Dibutyltin dilaurate (0.02 wt %) is then added to the solution usinga micropipette and the polymerization reaction is allowed to proceed.

After 1 hr, the ionic species precursor 2,2-bis(hydroxymethyl)propionicacid (0.79 g, 5.89 mmol) is added to the stirring solution and allowedto dissolve and react for 1 hr. After 1 hr, Fluorolink E10-H (2.78 g,1.40 mmol) is added to the stirring solution and allowed to react for 2hr at 100° C. The prepolymer is then allowed to cool down to roomtemperature. The prepolymer is diluted with tetrahydrofuran (12.75 mL)and placed in a plastic mixing container for centrifugal mixing.

In a separate vial, 1,4-butanediol (0.77 g, 8.54 mmol) is weighed anddiluted with tetrahydrofuran (0.5 mL). The two solutions are combined ina centrifugal mixer and mixed at 2300 rpm for 15 seconds. The polymer iscast from solution or sprayed using an airbrush to create a polyurethanefilm/coating.

Multiple samples are prepared, as follows. Sample E1 is unsoaked, sampleE2 is soaked in deionizied water, sample E3 is soaked in NaOH at pH=14,sample E4 is soaked in HCl at pH=2, and sample E5 includes copperacetate exposure during synthesis of the sample. Samples E1, E2, E3, E4,and E5 are then tested in accordance with Example F (friction testing)below.

Example F: Friction Testing of Samples

The change in friction in response to humidity is tested by firstequilibrating the coating samples of Examples A, B, C, D, and E atambient (40-55%) relative humidity or 85-90% relative humidity in ahumidity-controlled chamber. Then the coating samples are placed on avariable-angle stage and the angle is increased until a 5-gramcylindrical mass slides along the sample surface. The sliding angle isused to determine the friction constant (coefficient of friction).

The friction change is shown for the coating samples of Examples A-E inthe table of FIG. 2. Contact angles of water are also shown for samplesA, C1, C2, C3, C4, E1, E2, E3, E4, and E5. From the table in FIG. 2,sliding and coefficient-of-friction performance with differentembodiments of the technology versus controls can be observed.

The initial control (sample B) is produced from a PFPE and isocyanateprepolymer mixture that is cast from solution and allowed to cure underthe influence of atmospheric moisture. This composition has nohygroscopic component and shows a relatively higher coefficient offriction compared to other test samples at 85-90% relative humidity.Under the influence of increasing humidity, the coefficient of frictionincreased.

Examples B and C—linear thermoplastic polymer without and with ionicspecies, respectively—demonstrate the benefits of ionic charge oncoefficient of friction and its behavior under increasing humidity.Example B incorporates a triblock precursor molecule with PFPE as thecentral block and poly(ethylene glycol) blocks on the terminal ends.According to the data for sample B, a coating from this mixture produceslow coefficient of friction values but exhibits an increase incoefficient of friction with increased humidity.

The opposite is the case when ionic monomer species are introduced intothe chain backbone (Example C). Coefficient of friction in samples C1,C2, C3, or C4 begins at 0.19 near 50% relative humidity and decreases orstays constant with increasing humidity. This data also indicates that,at constant relative humidity, the coefficient of friction is reducedafter soaking the coating in water, HCl or Ca salt solutions. Thecoefficient of friction is as low as 0.13, for a 0.01 M Ca(OH)₂ soak ofthe coating then exposed to 85-90% relative humidity for the frictiontest.

Examples D and E use high-molecular-weight PEG as a first soft segmentcombined with a PFPE/PEG triblock as a second soft segment. Example Eincorporates ionic species, while Example D is a control sample with noionic species along the backbone. The system starts off at a highercoefficient of friction of 0.38 at 50% relative humidity, and withelevated humidity, the coefficient of friction increase to 0.62 (sampleD1). Soaking in deionizied water reverses this trend and causes a dropin coefficient of friction (sample D2). However, exposure to basicsolution conditions creates a situation that lowers coefficient offriction at 50% relative humidity while giving a dramatic (nearlytwo-fold) increase in coefficient of friction at 90% relative humidity(sample D3).

When carboxylic acid groups are incorporated into the backbone of thesepolymers (Example E), an overall decrease in the magnitude of thecoefficient of friction is observed for each sample compared to thecontrol sample, whether unsoaked (E1 versus D1), soaked in water (E2versus D2), or soaked in basic solution (E3 versus D3). The relativeincrease in coefficient of friction with increased humidity is reducedfor both the unsoaked and base-soaked sample.

Overall, these systems demonstrate the ability to be positivelyinfluenced through lower coefficient-of-friction performance by theincorporation of ionic species (free acid or charged species) along thechain backbone.

Vehicle-based cameras for surrounding awareness will require lenscoatings that will inhibit soiling in order to function. Once soiled,the camera will lose effectiveness and eventually cease functioning. Thecoatings/surfaces described herein may be used as camera lens coatings.

Aircraft lose efficiency from disruption of laminar flow when insect andparticulate debris collect on the aircraft wings. This inventionprovides materials that reduce the adhesion of insect and particulatedebris on aircraft surfaces, while simultaneously inhibiting theformation of ice.

Other practical applications for the present invention include, but arenot limited to, vehicle windows, optical lenses, filters, instruments,sensors, eyeglasses, cameras, satellites, and weapon systems. Forexample, automotive applications can utilize these coatings to preventthe formation of ice or debris on back-up camera lenses or back-upsensors. The principles taught herein may also be applied toself-cleaning materials, anti-adhesive coatings, corrosion-freecoatings, etc.

In this detailed description, reference has been made to multipleembodiments and to the accompanying drawings in which are shown by wayof illustration specific exemplary embodiments of the invention. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is to be understood thatmodifications to the various disclosed embodiments may be made by askilled artisan.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of theinvention. Additionally, certain steps may be performed concurrently ina parallel process when possible, as well as performed sequentially.

All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference in their entirety asif each publication, patent, or patent application were specifically andindividually put forth herein.

The embodiments, variations, and figures described above should providean indication of the utility and versatility of the present invention.Other embodiments that do not provide all of the features and advantagesset forth herein may also be utilized, without departing from the spiritand scope of the present invention. Such modifications and variationsare considered to be within the scope of the invention defined by theclaims.

What is claimed is:
 1. A segmented copolymer composition comprising: (a)one or more first soft segments selected from fluoropolymers having anaverage molecular weight from about 500 g/mol to about 20,000 g/mol,wherein said fluoropolymers are (α,ω)-hydroxyl-terminated and/or(α,ω)-amine-terminated; (b) one or more ionic species contained withinsaid soft segments and/or contained in copolymer chains that aredistinct from said soft segments; (c) one or more isocyanate species, ora reacted form thereof, possessing an isocyanate functionality of 2 orgreater; and (d) one or more polyol or polyamine chain extenders orcrosslinkers, or a reacted form thereof.
 2. The segmented copolymercomposition of claim 1, wherein said fluoropolymers are selected fromthe group consisting of polyfluoroethers, perfluoropolyethers,polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof. 3.The segmented copolymer composition of claim 2, wherein saidfluoropolymers include a fluoropolymer having the structure:

wherein: X=CH₂—(O—CH₂—CH₂)_(p)—OH wherein p=0 to 50; m=1 to 100; and n=1to
 100. 4. The segmented copolymer composition of claim 1, saidcomposition further comprising one or more second soft segments selectedfrom polyesters or polyethers, wherein said polyesters or polyethers are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated.
 5. Thesegmented copolymer composition of claim 4, wherein the molar ratio ofsaid second soft segments to said first soft segments is less than 2.0.6. The segmented copolymer composition of claim 4, wherein saidpolyesters or polyethers are selected from the group consisting ofpoly(oxymethylene), poly(ethylene glycol), poly(propylene glycol),poly(tetrahydrofuran), poly(glycolic acid), poly(caprolactone),poly(ethylene adipate), poly(hydroxybutyrate), poly(hydroxyalkanoate),and combinations thereof.
 7. The segmented copolymer composition ofclaim 1, wherein said ionic species are contained chemically within saidfirst soft segments.
 8. The segmented copolymer composition of claim 1,wherein said ionic species are present as, or in, polymer-chain pendantgroups within said first soft segments.
 9. The segmented copolymercomposition of claim 1, wherein said ionic species are containedchemically in hard segments containing said reacted form of said one ormore isocyanate species.
 10. The segmented copolymer composition ofclaim 1, wherein said ionic species are contained chemically incopolymer chains that are distinct from each of said first softsegments, said second soft segments, and hard segments containing saidreacted form of said one or more isocyanate species.
 11. The segmentedcopolymer composition of claim 1, wherein said ionic species are(α,ω)-hydroxyl-terminated and/or (α,ω)-amine-terminated.
 12. Thesegmented copolymer composition of claim 1, wherein said ionic speciesincludes a cationic species possessing a charge of +1 or more.
 13. Thesegmented copolymer composition of claim 1, wherein said ionic speciesincludes an anionic species possessing a charge of −1 or more negative.14. The segmented copolymer composition of claim 1, wherein said ionicspecies includes an ionizable salt or other ionizable molecule.
 15. Thesegmented copolymer composition of claim 1, wherein said ionic speciesincludes a zwitterionic component.
 16. The segmented copolymercomposition of claim 1, wherein said ionic species includes apolyelectrolyte.
 17. The segmented copolymer composition of claim 1,wherein said ionic species includes an ionomer.
 18. The segmentedcopolymer composition of claim 1, wherein said ionic species areselected from the group consisting of (2,2-bis-(1-(1-methylimidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.
 19. The segmented copolymercomposition of claim 1, wherein said isocyanate species is selected fromthe group consisting of 4,4′-methylenebis(cyclohexyl isocyanate),hexamethylene diisocyanate, cycloalkyl-based diisocyanates,tolylene-2,4-diisocyanate, 4,4′-methylenebis(phenyl isocyanate),isophorone diisocyanate, and combinations or derivatives thereof. 20.The segmented copolymer composition of claim 1, wherein said polyol orpolyamine chain extenders or crosslinkers have an average functionalityof at least
 3. 21. The segmented copolymer composition of claim 1,wherein said one or more polyol or polyamine chain extenders orcrosslinkers are selected from the group consisting of 1,3-butanediol,1,4-butanediol, 1,3-propanediol, 1,2-ethanediol, diethylene glycol,triethylene glycol, tetraethylene glycol, propylene glycol, dipropyleneglycol, tripropylene glycol, neopentyl glycol, 1,6-hexane diol,1,4-cyclohexanedimethanol, ethanol amine, diethanol amine,methyldiethanolamine, phenyldiethanolamine, glycerol,trimethylolpropane, 1,2,6-hexanetriol, triethanolamine, pentaerythritol,ethylenediamine,1,3-propanediamine, 1,4-buatendiamine,diethyltoluenediamine, dimethylthiotoluenediamine, isophoronediamine,diaminocyclohexane, N,N,N′,N′-tetrakis (2-hydroxypropyl)ethylenediamine, and homologues, combinations, derivatives, or reactionproducts thereof.
 22. The segmented copolymer composition of claim 1,wherein said composition contains, in a hard segment, said reacted formof said one or more isocyanate species, combined with said reacted formof said one or more polyol or polyamine chain extenders or crosslinkers.23. The segmented copolymer composition of claim 1, wherein saidsegmented copolymer composition is present in a coating.
 24. Ananti-fouling coating comprising: a substantially continuous matrixcontaining a first component; and a plurality of inclusions containing asecond component, wherein said inclusions are dispersed within saidmatrix; wherein one of said first component or said second component isa low-surface-energy polymer having a surface energy between about 5mJ/m² to about 50 mJ/m², and the other of said first component or saidsecond component is a hygroscopic material containing one or more ionicspecies, wherein said low-surface-energy polymer and said hygroscopicmaterial are chemically connected ionically or covalently, and whereinsaid continuous matrix and said inclusions form a lubricating surfacelayer in the presence of humidity.
 25. The anti-fouling coating of claim24, wherein said low-surface-energy polymer is a fluoropolymer selectedfrom the group consisting of polyfluoroethers, perfluoropolyethers,polyfluoroacrylates, polyfluorosiloxanes, and combinations thereof. 26.The anti-fouling coating of claim 24, wherein said ionic species isselected from the group consisting of (2,2-bis-(1-(1-methylimidazolium)-methylpropane-1,3-diol bromide),1,2-bis(2′-hydroxyethyl)imidazolium bromide,(3-hydroxy-2-(hydroxymethyl)-2-methylpropyl)-3-methyl-1H-3λ⁴-imidazol-1-iumbromide, 2,2-bis(hydroxymethyl)butyric acid,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid,N-methyl-2,2′-iminodiethanol, 3-dimethylamino-1,2-propanediol,2,2-bis(hydroxymethyl)propionic acid, 1,4-bis(2-hydroxyethyl)piperazine,2,6-diaminocaproic acid, N,N-bis(2-hydroxyethyl)glycine,2-hydroxypropanoic acid hemicalsium salt, dimethylolpropionic acid,N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine,N-benzyldiethanolamine, N-t-butyldiethanolamine, bis(2-hydroxyethyl)benzylamine, bis(2-hydroxypropyl) aniline, and homologues, combinations,derivatives, or reaction products thereof.
 27. The anti-fouling coatingof claim 26, wherein said hygroscopic material consists essentially ofsaid ionic species.
 28. The anti-fouling coating of claim 24, whereinsaid hygroscopic material includes a material selected from the groupconsisting of poly(acrylic acid), poly(ethylene glycol),poly(2-hydroxyethyl methacrylate), poly(vinyl imidazole),poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline),poly(vinylpyrolidone), cellulose, modified cellulose, carboxymethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose, hydrogels, PEG diacryalate, monoacrylate, and combinationsthereof.
 29. The anti-fouling coating of claim 24, wherein saidlow-surface-energy polymer and said hygroscopic material are covalentlyconnected in a block copolymer.
 30. The anti-fouling coating of claim24, wherein said coating further comprises one or more additionalcomponents selected from the group consisting of a particulate filler, asubstrate adhesion promoter, a pigment, a dye, a plasticizer, aflattening agent, and a flame retardant.